The invention is directed to the treatment of various skin disorders with high-strength tretinoin (also known as vitamin A acid or all-trans retinoic acid). More particularly, the invention is directed to the treatment of skin disorders, especially of human facial skin, with amounts of tretinoin sufficient to induce desquamation of the skin to ameliorate the disorder.
Caucasians who have had a good deal of sun exposure in childhood will show the following gross cutaneous alternations in adult life: wrinkling, leatheriness, yellowing, looseness, roughness, dryness, mottling (hyperpigmentation) and various premalignant growths (often subclinical). These changes are most prominent in light-skinned persons who burn easily and tan poorly. The baleful effects of sunlight are cumulative, increasing with time and often referred to as "photoaging". Although the anatomic degradation of the skin is most advanced in the elderly, the destructive effects of excessive sun exposure are already evident by the second decade. Serious microscopic alterations of the epidermis and dermis occur decades before these become clinically visible. Wrinkling, yellowing, leatheriness, loss of elasticity are very late changes.
Retinoids (e.g., Vitamin A and its derivatives) are substances which are known to have a broad spectrum of biological activity. More specifically, these substances affect cell growth, differentiation and proliferation. Retinoids affect the differentiation, maintenance, and proliferation of many types of cells whether they are of ectodermal, endodermal or mesodermal origin; whether they are epithelial, fibroblastic or mesenchymal; or whether they are neoplastic, preneoplastic or non-neoplastic. Retinoids have found clinical utility in the treatment of severe cystic acne, psoriasis, and other disorders of keratinization. Possible uses of retinoids are being explored in the prophylaxis and treatment of cancer. For a recent review of developments in the uses of retinoids, see Orfanos et al., "Current Use and Future Potential Role of Retinoids in Dermatology," Drugs 53:358-380 (March 1997).
Other older reviews of the uses of retinoids in research and clinical medicine can be found in the publication of a symposium held in Geneva: J. H Saurat, Editor, "Retinoids: New Trends in Research and Therapy", Karger Publishing Co. (1985); Pawson, B. A. et al., "Retinoids at the Threshold: Their Biological Significance and Therapeutic Potential", Journal of Medicinal Chemistry 25:1269-1277 (1982); and Thomas, J. R., et al., "The Therapeutic Uses of Topical Tretinoin", Journal of American Academy of Dermatology 4:505-516 (1981).
It is known to use tretinoin topically for treatment of acne as set forth in U.S. Pat. No. 3,729,568 of A. M. Kligman. That patent discloses the treatment of acne with tretinoin in alcohol/glycol vehicles at concentrations sufficient to cause irritation including inflammation and peeling, such concentrations ranging as high as 0.5 weight percent, preferably 0.05 to 0.25 weight percent.
U.S. Pat. Nos. 4,603,146; 4,877,805 and 4,888,342 of A. M. Kligman disclose long term methods for treating sun-damaged human skin topically with low concentrations of tretinoin and other retinoids in an emollient vehicle, such amounts of retinoids being essentially non-irritating to the skin. This treatment requires periodic applications for several months before improvement is achieved, and this factor often leads to the treated individual discontinuing treatment before positive results are obtained.